#include
template
LockFreeQueue() : head_(new Node), tail_(head_.load()) {}~LockFreeQueue() {while (Node* const old_head = head_->next_) {delete head_;head_ = old_head;}delete head_;}void push(const T& value) {auto new_node = std::make_unique<Node>(value);Node* old_tail = tail_.exchange(new_node.get(), std::memory_order_acq_rel);old_tail->next_.store(new_node.release(), std::memory_order_release);size_.fetch_add(1, std::memory_order_release);}bool try_pop(T& value) {Node* old_head = head_.load(std::memory_order_relaxed);for (;;) {Node* const new_head = old_head->next_.load();if (new_head == nullptr) {return false;}if (head_.compare_exchange_weak(old_head, new_head, std::memory_order_acquire)) {value = new_head->value_;size_.fetch_sub(1, std::memory_order_release);delete old_head;return true;}}}bool empty() const {return size_.load(std::memory_order_acquire) == 0;}
private:
struct Node {T value_;std::atomic<Node*> next_;Node() : next_(nullptr) {}explicit Node(const T& value) : value_(value), next_(nullptr) {}};std::atomic<Node*> head_;std::atomic<Node*> tail_;std::atomic<size_t> size_{0};
};
